Definition Sterilization techniques include all the means used to completely eliminate or destroy living microorganisms on any object, including tools used to test or treat patients. Purpose The term microorganism, or microbe, refers to any single-celled living organism, including bacteria, viruses, and fungi. (Though viruses are not true single-celled organisms, medical science still usually classifies them as microorganisms.) Microbes can be transferred by direct contact or indirectly through a vehicle (like a surgical tool) or via the air the patient breathes. Sterilization Techniques Steam Sterilization.Among sterilization methods, steam sterilization, which is dependable and economical, is the most widely used for wrapped and unwrapped critical and semicritical items that are not sensitive to heat and moisture. Prevacuum sterilizers are fitted with a pump to create a vacuum in the chamber and ensure air removal from the sterilizing chamber before the chamber is pressurized with steam Unsaturated Chemical-Vapor Sterilization. Unsaturated chemical-vapor sterilization involves heating a chemical solution of primarily alcohol with 0.23% formaldehyde in a closed pressurized chamber. Unsaturated chemical vapor sterilization of carbon steel instruments (e.g., dental burs) causes less corrosion than steam sterilization because of the low level of water present during the cycle Dry-Heat Sterilization.Dry heat is used to sterilize materials that might be damaged by moist heat (e.g., burs and certain orthodontic instruments). Although dry heat has the advantages of low operating cost and being noncorrosive, it is a prolonged process and the high temperatures required are not suitable for certain patient-care items and devices. Dry-heat sterilizers used in dentistry include static-air and forced-air types.• The static-air type is commonly called an oven-type sterilizer. Heating coils in the bottom or sides of the unit cause hot air to rise inside the chamber through natural convection.• The forced-air type is also known as a rapid heat-transfer sterilizer. Heated air is circulated throughout the chamber at a high velocity, permitting more rapid transfer of energy from the air to the instruments, thereby reducing the time needed for sterilization. Sterilization of Unwrapped Instruments.An unwrapped cycle (sometimes called flash sterilization) is a method for sterilizing unwrapped patient-care items for immediate use. The time required for unwrapped sterilization cycles depends on the type of sterilizer and the type of item (i.e., porous or nonporous) to be sterilized. Unwrapped sterilization should be used only under certain conditions: 1) thorough
cleaning and drying of instruments precedes the unwrapped sterilization cycle; 2)mechanical monitors are checked and chemical indicators used for each cycle; 3) care istaken to avoid thermal injury to DHCP or patients; and 4) items are transportedaseptically to the point of use to maintain sterility (134,258,262). Because all implantabledevices should be quarantined after sterilization until the results of biological monitoringare known, unwrapped or flash sterilization of implantable items is not recommended.Other Sterilization Methods: Heat-sensitive critical and semicritical instruments and devices can be sterilized byimmersing them in liquid chemical germicides registered by FDA as sterilants. Whenusing a liquid chemical germicide for sterilization, certain poststerilization procedures areessential. Items need to be 1) rinsed with sterile water after removal to remove toxic orirritating residues; 2) handled using sterile gloves and dried with sterile towels; and 3)delivered to the point of use in an aseptic manner. If stored before use, the instrumentshould not be considered sterile and should be sterilized again just before use. In addition,the sterilization process with liquid chemical sterilants cannot be verified with biologicalindicators (263).Because of these limitations and because liquid chemical sterilants can requireapproximately 12 hours of complete immersion, they are almost never used to sterilizeinstruments. Rather, these chemicals are more often used for high-level disinfection.Shorter immersion times (12--90 minutes) are used to achieve high-level disinfection ofsemicritical instruments or items. These powerful, sporicidal chemicals (e.g.,glutaraldehyde, peracetic acid, and hydrogen peroxide) are highly toxic. Manufacturerinstructions (e.g., regarding dilution, immersion time, and temperature) and safetyprecautions for using chemical sterilants/high-level disinfectants must be followedprecisely. These chemicals should not be used for applications other than those indicatedin their label instructions. Misapplications include use as an environmental surfacedisinfectant or instrument-holding solution.Low-temperature sterilization with ethylene oxide gas (ETO) has been used extensivelyin larger health-care facilities. Its primary advantage is the ability to sterilize heat- andmoisture-sensitive patient-care items with reduced deleterious effects. However, extendedsterilization times of 10--48 hours and potential hazards to patients and DHCP requiringstringent health and safety requirements (272--274) make this method impractical forprivate-practice settings. Handpieces cannot be effectively sterilized with this methodbecause of decreased penetration of ETO gas flow through a small lumen (250,275).Other types of low-temperature sterilization (e.g., hydrogen peroxide gas plasma) existbut are not yet practical for dental offices.Bead sterilizers have been used in dentistry to sterilize small metallic instruments (e.g.,endodontic files). FDA has determined that a risk of infection exists with these devicesbecause of their potential failure to sterilize dental instruments and has required theircommercial distribution cease unless the manufacturer files a premarket approvalapplication. If a bead sterilizer is employed, DHCP assume the risk of employing a dentaldevice FDA has deemed neither safe nor effective.Sterilization Monitoring. Monitoring of sterilization procedures should include acombination of process parameters, including mechanical, chemical, and biological.These parameters evaluate both the sterilizing conditions and the procedureseffectiveness.
Aseptic techniqueIt has been known since the days of Florence Nightingale that clean surroundings aredefinitely less conducive to the growth of microorganisms than unclean ones. Thecreation of sterile environments always includes scrupulous cleanliness. The use ofdisinfectants in washing furniture, walls and floors, as well as in soaking medicalequipment or other patient-care items is another important measure. Disinfectants areharsh chemical compounds described as bactericidal (capable of killing bacteria), orbacteriostatic (capable of stopping the growth or reproduction of bacteria). Some of thesedisinfectants may also be antiviral agents or antifungal. Disinfectants are usually too toxicto tissue to be used directly on the body.Antiseptics are chemical compounds that are also either bactericidal or bacteriostatic. Butthese are usually more diluted solutions and can safely be used in direct contact withhuman tissues. Common antiseptics include iodine, hydrogen peroxide, and thimerosal.